Generally, in operation of a fireproof door lock, a press handle in a handle frame of the fireproof doorplate is pressed so that the lock stud in the lock casing is reduced inwards. Thus the door lock will release and thus is opened. However the handle slides along an inclined recess track at one of two sides of a retaining seat in the handle frame seat. The user must apply a great force and only the vertical component of the force is effective. Furthermore, if the force is too great, the lock will be locked.
Besides, no structure can provide proper restoring force to the retaining seat, when it is desired to close an opened lock, the operation is not smooth.